1. Field of the Invention
This invention relates to couplings and more particularly to means for connecting a control line disposed interiorily of a wellhead element to a hydraulic line located exteriorly of the wellhead element.
2. Description of the Prior Art
In well completion equipment it is often found necessary to actuate a mechanism, such as a valve or the like, disposed within the well. The actuating means is generally powered by a hydraulic fluid in a pipe line or conduit extending down to the mechanism from the top of the well, e.g. from a source of pressurized hydraulic fluid on an above water platform in the case of a subsea well.
The hydraulic fluid conduit or control line that extends from the mechanism to the top of the well is usually a small diameter pipe, e.g. 1/2 to 1 inch in outer diameter, disposed outside of the tubing suspended within the well from a tubing hanger. The tubing hanger is supported by a wellhead element or tubing head. Such a hydraulic fluid conduit or control line is generally threaded into a socket in the lower end of a longitudinal passage extending up through the body of the tubing hanger. At a suitable level a transverse passage extending horizontally, e.g. radially from the longitudinal axis of the well, within the tubing hanger communicates with the longitudinal passage within the tubing hanger to provide a fluid passage from the radial periphery of the tubing hanger to the control line. A radially extending bore is provided through the wall of the tubing head for alignment with the horizontal passage of the tubing hanger continuing the fluid passage to the exterior periphery of the wellhead element for connection with the hydraulic fluid line coming from a source of fluid under pressure.
The nature of the environment and of the equipment creates an alignment problem between the tubing head bore and the tubing hanger passage. The equipment and apparatus is large and bulky and is difficult to rotate once installed. Further several thousand feet of tubing is suspended from the tubing hanger. These factors make it hard to align the tubing hanger with respect to the tubing head. It is also difficult to manufacture such apparatus whereby even if the hanger and head were properly oriented that the bore and passage would be coaxial.
In the above described construction there exists the further objection that upon the attempted installation of prior art couplings leakage will occur at the connection between the hydraulic line and the tubing hanger due to improper alignment. Improper alignment further increases the possibility of leakage of well fluids between the coupling and the tubing head.
Another objection to the earlier couplings is the use of a slip fit connection between the coupling and the tubing hanger since such a connection requires a resilient seal. A resilient seal is not desirable due to the shortness of the life of the seal and to the lack of strength and corrosive resistance of the seal as compared to a metal-to-metal seal.